The present invention relates to a vehicle-mounted terminal for generating a cipher key for security protection.
Electronization of vehicle-mounted terminals has progressed in the field of vehicles because of an increased demand for safety, good environments and ease of use. For example, a hybrid car mounts not only a conventional gasoline engine but also an electronic motor and an inverter which are important electronic components cooperating with the gasoline engine. In-vehicle networks such as a controller area network (CAN) and a local interconnect network (LIN) are also prevailing in order to realize cooperation between electronic control units (ECUs) for controlling vehicle electronic components. Use of VRM terminals is expanding which terminals are used for collecting vehicle information via an in-vehicle network and storing the vehicle information in a storage medium such as a memory and a hard disc drive (HDD), in order to confirm thereafter trouble information and event information. VRM (an acronym for vehicle relationship management) is a technique of increasing an added value of a vehicle by providing new services such as remote maintenance by collecting, accumulating and utilizing vehicle information.
If vehicle information relates to vehicle control/diagnosis and driver behavior, security of collected data is often required so that ciphering is necessary for security protection. In order to retain sufficient safety, a general information system generates dynamically at each site a random number as a cipher key. It is known that a random number includes an “arithmetic random number (pseudo random number)” obtained from a predetermined algorithm and a “physical random number” obtained from physical phenomena.
As a technique of generating an arithmetic random number, JP-A-10-247140 describes a technique that a bit string generated by a 16-bit free-running counter is sequentially shifted by 16 bits to right and a new freerun count is loaded to left end 16 bits to thereby generate a long random number with small scale hardware. As a technique of generating a physical random number, JP-A-2001-005383 describes a technique that a random number is generated from an output value of a temperature sensor unable to be predicted from an external.